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Burnham-On-Sea History > 1607
Flood
1607
Flood in the Bristol Channel - Was it a UK tsunami?
Research
into the devastating 1607 flood that affected Burnham-On-Sea and the
Bristol Channel in January 1607 has, since 2002, been the subject of
a study between Dr Simon Haslett, Head of Geography at Bath Spa University
College, author of Coastal Systems and Dr Ted Bryant, School
of Geosciences at the University of Wollongong, Australia, author of
Tsunami: the Underrated Hazard.
The flood
occurred around 9am on the '20th January 1606', although in the modern
calendar this is the 30th January 1607. The event is recorded on plaques
in a number of churches, including those at Kingston Seymour in Somerset,
and in Monmouthshire at Goldcliff, St. Brides, Redwick and Peterstone.
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The breaking of the sea bank at Burnham-On-Sea led to some 30
villages being utterly inundated, and their cattle destroyed,
and men, women and children besides. The accounts state that 28
people were drowned at Huntspill and 26 at Brean, a death toll
that was repeated in many other villages.
At Appledore, Devon,
a 60 tonne ship was well-laden and ready to sail and was driven
by the wave onto marshy ground well above high tide, likely never
to be recovered.
In Barnstaple, Devon,
the wave burst open doors that were locked and bolted and knocked
down many walls and houses, one of which was the house of a James
Frost in that the roof and walls collapsed and killed both him
and two of his children.
Near Newport, Gwent,
a wealthy women, Mistress Van, lived four miles from the sea and
although she saw the wave approaching from her house she could
not get upstairs before it rushed through and drowned her.
In Monmouthshire, "a
maide child, not passing the age of foure years: it is reported
that the mother thereof, perceiving the waters to breake so fast
into her house, and not being able to escape with it, and having
no clothes on, set it upon a beame in the house, to save it from
being drowned. And the waters rushing in a pace, a little chicken
as it seemeth, flew up unto it [the child], (it being found in
the bosome of it, when helpe came to take it [the child] downe)
and by the heate thereof, as it is thought, preserved the childe's
life".
In Monmouthshire, "Another
little childe is affirmed to have been cast uppon land in a cradle,
in which was nothing but a catte [cat], the which was discerned
as it came floating to the shoare, to leape still from one side
of the cradle unto the other, even as if she had been appointed
steresman to preserve the small barke from the waves furie".
In Monmouthshire, "A
certain man and woman having taken a tree for their succour, espying
nothing but death before their eyes, at last among other things
which were carried along, they perceived a certain tubbe of great
bignesse to come nearer and nearer unto them, until it rested
upon that tree wherein they were, committed themselves, and were
carried safe until they were cast upon the drie shore".
In Monmouthshire, "more
than did, had perished for want of food, and extreme cold, had
not the Rt. Honble. Lord Herbert .... sent out boats to relieve
the distresse .... himself goping to such houses as he could minister
to their provision of meate and other necessaries".
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The Kingston
Seymour plaque reads: "An inundation of the sea water by overflowing
and breaking down the Sea banks; happened in this Parish of Kingstone-Seamore,
and many others adjoining; by reason whereof many Persons were drown'd
and much Cattle and Goods, were lost: the water in the Church was five
feet high and the greatest part lay on the ground about ten days. WILLIAM
BOWER"
The idea
that the 1607 flood was due to a tsunami was first put forward by Haslett
and Bryant in a scientific paper published in 2002 in the journal Archaeology
in the Severn Estuary.
A number
of historical documents exist that describe the event and its aftermath.
An area from Barnstaple in north Devon, up the Bristol Channel and Severn
Estuary to Gloucester, then along the South Wales coast around to Cardigan
was affected, some 570 km of coastline.
The coastal
population was devastated with at least 2,000 fatalities according to
one of the contemporary sources.
In some
parts of the coast the population never recovered from the social and
economic disaster.
Haslett
and Bryant were led to think that the 1607 flood was caused by a tsunami,
rather than a storm, for a number of reasons:
1. Some historical accounts indicate that the weather was fine e.g.
"for about nine of the morning, the same being most fayrely and
brightly spred, many of the inhabitants of these countreys prepared
themselves to their affayres" and the ship at Appldedore (see above)
is unlikely to be ready to sail in stormy weather.
2. The sea appears to have been "driven back" i.e. retreated
out to sea, before the wave struck, a classic tsunami herald.
3. The wave appeared as "mighty hilles of water tombling over one
another in such sort as if the greatest mountains in the world had overwhelmed
the lowe villages or marshy grounds. Sometimes it dazzled many of the
spectators that they imagined it had bin some fogge or mist coming with
great swiftness towards them and with such a smoke as if mountains were
all on fire, and to the view of some it seemed as if myriads of thousands
of arrows had been shot forth all at one time."
This is very similar to descriptions of more recent tsunami, such as
the tsunami associated with the eruption of Krakatau in 1883, where
accounts refer to the sea as being 'hilly', and the reference to dazzling,
fiery mountains, and myriads of arrows, is reminiscent of accounts of
tsunami on the Burin Peninsula (Newfoundland) in 1929, where the wave
crest was shining like car headlights, and in Papua New Guinea in 1998
where the wave was frothing and sparkling.
4. The
speed of the wave appears to have been faster than a storm flood as
the wave is 'affirmed to have runne …. with a swiftness so incredible,
as that no gray-hounde could have escaped by running before them'.
In the
summer of 2004, Haslett and Bryant embarked on field work in the area
to record any physical impacts of the proposed 1607 tsunami that might
still be left in the landscape. They found:
Erosion of rock at the coast
that is characteristic of erosion caused by high velocity water flow.
This includes two large chunks of farmland on the Severn Estuary north
of Bristol that were simply washed away, one where the foundation of
the Second Severn Crossing is, and the other is now the reservoir for
the Oldbury Nuclear Power Station;
The deposition of layers
of sand over wide areas at the time, discovered in boreholes in the
ground from north Devon to Gloucestershire to the Gower;
Large boulders that are only
easily moved by tsunami waves have been found stacked like dominoes
at and above the high tide limits all along the coast.
These signatures
of tsunami enable Haslett and Bryant to estimate the scale of the proposed
tsunami wave and its affects.
Tsunami
height - In the open sea area between north Devon and Pembrokeshire,
the wave was just under 4m (13ft) high, but as it entered the constricting
funnel-shaped Bristol Channel and Severn Estuary, the wave increased
in height to 5m (16ft) along the Glamorgan coast, 5.5m (18ft) along
the Somerset coast, and over 7.5m (25ft) high, by the time it reached
the Monmouthshire coast. This increase in wave height due to the funnel-shape
of the estuary is exactly the same as the process that creates the famous
Severn Bore.
Tsunami speed - The speed (velocity)
of a tsunami is related to its height, so as it moved up estuary and
got squeezed between the opposing shores of England and Wales, it got
faster, striking the coast at just over 12 m/sec (27mph) in north Devon
and southwest Wales, to just under 14 m/sec (31mph) along the Glamorgan
coast, to 14.5 m/sec (32mph) in Somerset, and over 17 m/sec (38mph)
in Monmouthshire. This agrees well with the contemporary observations
regarding the speed of the wave.
Tsunami inundation - On the flat
coastal areas the tsunami was able to penetrate a considerable distance
inland. The maximum inland penetration possible of a moving tsunami
wave in north Devon and southwest Wales would have been just under 2.5
km (1.55 miles), in Glamorgan just over 3 km (1.86 miles), in Somerset
just under 4 km (2.5 miles), and in Monmouthshire just under 6 km (3.7
miles). This agrees well with the accounts of the wave reaching up to
4 miles inland at Cardiff and in Monmouthshire. The fact that the floodwaters
reached further inland in places, such as to the foot of Glastonbury
Tor (14 miles inland) is due to the fact that the landsurface actually
slopes landward in many of the coastal wetland areas, such as the Somerset
Levels, so once the wave collapsed the water flowed landward under gravity
rather than back to the sea.
A possible
cause of the proposed tsunami is not yet known, but the possibilities
include a landslide off the continental shelf between Ireland and Cornwall,
or an earthquake along an active fault system in the sea south of Ireland.
This fault system has apparently experienced an earthquake greater than
magnitude 4 on the Richter scale within the last 20 years, so the chance
of a bigger tsunami earthquake is a possibility. It may also have been
a combination, in that an earthquake might have triggered a submarine
slide.
This
article was adapted from the findings of a Bath
Spa University College study issued
by Dr Simon Haslett FGS, FRGS.
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